This measurement is captured on an external USB flash drive. The captured data file cannot be recalled and displayed on the instrument screen.
The LMR Master can capture and log P25 IQ data to a USB flash drive.
1. From the Frequency main menu, set the receiver frequency (Rx Freq).
2. From the Setup main menu, choose a Mod Type.
For C4FM modulation, interleaved Delta Phase data then Magnitude data is captured. For CQPSK modulation, interleaved I data then Q data is captured.
3. Insert a formatted USB flash drive into the LMR Master and from the Measurement main menu, press the P25 IQ Capture submenu key. After approximately 10 seconds, the instrument displays a message that the capture is complete.
The IQ data is sampled at 4,800 x 11 symbols per second. The saved file has an ASCII header and binary data (Figure: IQ Capture (CQPSK Modulation)). The data is written in 24‑bit two’s complement integers format. The header includes “SampleType” (I/Q for CQPSK or DeltaPhase/Mag for C4FM). The file is intended for post‑processing in MATLAB or other data analysis software.
The file will be written to a data stamped folder inside the /usr folder on the root level of the USB flash drive. The file is named:
IQ_CAPTUREyearmonthdaytime.p25
Note
There is no display menu for P25 IQ Capture. The LMR Master will continue to display the previous measurement screen during IQ Capture.
